1. Department of Physics, Chung Yuan Christian University, No. 200, Zhongbei Rd., Zhongli, Taoyuan 320314, Taiwan
2. Department of Photonics, National Cheng Kung University, No. 1, University Rd., Tainan 701401, Taiwan
3. Department of Physics, National Central University, No. 300, Zhongda Rd., Zhongli, Taoyuan 320317, Taiwan
4. Department of Chemical Engineering and Material Science, Yuan Ze University, No. 135, Yuandong Rd., Zhongli, Taoyuan 320315, Taiwan